Proteins, controlled release, polymer systems

Self-assembly of polymers in the bulk Polymer micelles, polymero-somes, gelled macromole-cules, nano-tubes, protein fibres/tapes produced by aggregation at low pH, controlled release vehicles, smart delivery systems 50-500 nm Forster and Konrad, 2003 Sanguansri and Augustin, 2006 Dickinson 2006a Graveland-Bikker and de Kruif, 2006 van der Linden, 2006... 

Cappello, J., Crissman, J. W., Crissman, M., Ferrari, F. A., Textor, G., Wallis, O., Whidedge, J. R., Zhou, X., Burman, D., Aukerman, L., and Stedronsky, E. R. (1998). In-situ self-assembling protein polymer gel systems for administration, delivery, and release of drugs. /. Control. Release 53, 105-117. 

A sustained drug release is favourable for drugs with short elimination half-life. It can be controlled by hydration and diffusion mechanisms or ionic interactions between the drug and the polymeric carrier. In the case of diffusion control the stability of the carrier system is essential, as its disintegration leads to a burst release. Therefore, the cohesiveness of the polymer network plays a crucial role in order to control the release over several hours. Due to the formation of disulphide bonds within the network thiomers offer adequate cohesive stability. Almost zero-order release kinetics could be shown for insulin embedded in thiolated polycarbophil matrices (Clausen and Bernkop-Schnurch 2001). In the case of peptide and protein drugs release can be controlled via ionic interactions. An anionic or cationic polymer has to be chosen depending... 

Polyelectrolyte complexes can be used as implants for medical use, as microcapsules, or for binding of pharmaceutical products, including proteins. In recent years, a new class of organometallic polymers, polyphosphazenes, has become available. Synthetic flexibility of polyphosphazenes makes them a suitable material for controlled-release technologies. Desirable characteristics of a polymeric system used for drug delivery are as follows ... 

Some of the most promising systems for the controlled release of proteins and peptides involve encapsulation or entrapment in biocompatible polymeric materials. The most widely used polymers to date are poly(ethylene glycol) (PEG), (D,L)-poly(lactic glycohc acid) (PLGA), poly(lactic acid) (PLA) and chitosan. Polymers could be attached to the protein to incTease the overall molecular weight of the system and so reduce the rate of absorption across the epithehum of the alveoh, or the protein could be encapsulated in the polymeric system and slowly released into systemic circulation. 

Bezemer JM, Grijpma DW, Dijkstra PJ, Van Bhtterswijk CA, Feijen J. A controlled release system for proteins based on poly(ether-ester) block-copolymers polymer network characterization. J Control Release 1999 62 393—405. 

Polymers are mainly classified into two categories, natural and synthetic polymers (Table 30.1). Natural (water soluble) polymers are mostly obtained from natural sources. Naturally derived polymers with special focus on polysaccharides and proteins have become attractive in the biological applications of controlled release systems. Polysaccharides are a class of biopolymers constituted by either one or two alternating monosaccharides, which differ in their monosaccharide units in the length of a chain, in the types of the linking units, and in the degree of branching. ... 

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